Re: Proposal: Conflict log history table for Logical Replication

On Wed, Sep 24, 2025 at 4:00 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Tue, Sep 23, 2025 at 11:29 PM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
> >
> > On Sat, Sep 20, 2025 at 4:59 AM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> >
> > >
> > > AFAIR, one open point for internally created tables is whether we
> > > should skip changes to conflict_history table while replicating
> > > changes? The table will be considered under for ALL TABLES
> > > publications, if defined? Ideally, these should behave as catalog
> > > tables, so one option is to mark them as 'user_catalog_table', or the
> > > other option is we have some hard-code checks during replication. The
> > > first option has the advantage that it won't write additional WAL for
> > > these tables which is otherwise required under wal_level=logical. What
> > > other options do we have?
> >
> > I think conflict history information is subscriber local information
> > so doesn't have to be replicated to another subscriber. Also it could
> > be problematic in cross-major-version replication cases if we break
> > the compatibility of history table definition.
> >
>
> Right, this is another reason not to replicate it.
>
> > I would expect that the
> > history table works as a catalog table in terms of logical
> > decoding/replication. It would probably make sense to reuse the
> > user_catalog_table option for that purpose. If we have a history table
> > for each subscription that wants to record the conflict history (I
> > believe so), it would be hard to go with the second option (having
> > hard-code checks).
> >
>
> Agreed. Let's wait and see what Dilip or others have to say on this.

Yeah I think this makes sense to create as 'user_catalog_table' tables
when we internally create them. However, IMHO when a user provides
its own table, I believe we should not enforce the restriction for
that table to be created as a 'user_catalog_table' table, or do you
think we should enforce that property?

--
Regards,
Dilip Kumar
Google